Systems and Methods for Visualizing Ablated Tissue

ABSTRACT

Systems and methods for visualizing ablated tissue are disclosed. In some embodiments, a system for imaging tissue comprising: a catheter having a distal end and a proximal end; an inflatable balloon disposed about the distal end of the catheter; and an optical housing extending from the distal end of the catheter into the balloon, the optical housing being configured to position inside the balloon a light source for illuminating a tissue outside the balloon and a camera for imaging the illuminated tissue.

RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 13/624,902, filed Sep. 22, 2012, which is a continuation-in-part ofU.S. application Ser. No. 13/624,899, filed on Sep. 22, 2012, and claimsthe benefit of and priority to U.S. Provisional Application Ser. No.61/537,798, filed on Sep. 22, 2011, and the entirety of theseapplications are hereby incorporated herein by reference.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with Government support under Grant/Contract No.R01 HL095828 awarded by the National Institutes of Health. TheGovernment has certain rights in this invention.

FIELD

The embodiments disclosed herein relate to methods and systems forablation and visualization of tissue.

BACKGROUND

Exemplary embodiments are directed to techniques used during thetreatment of Atrial Fibrillation (AF). Atrial fibrillation is the mostcommon sustained arrhythmia, which currently affects two millionAmericans. Atrial fibrillation is associated with increased mortality,morbidity and an impaired quality of life, and is an independent riskfactor for stroke. The substantial lifetime risk of developing atrialfibrillation underscores the public health burden of the disease, whichin the United States alone amounts to an annual treatment cost exceeding$7 billion.

Eighty-five percent of episodes in patients with atrial fibrillation areknown to be triggered by focal electrical activity originating fromwithin muscle sleeves that extend into the Pulmonary Veins (PV). Atrialfibrillation may also be triggered by focal activity within the superiorvena cava or other atrial structures. These focal triggers can causeatrial tachycardia that is driven by reentrant electrical activity androtors, which may then fragment into a multitude of electrical waveletsthat are characteristic of atrial fibrillation. Prolonged atrialfibrillation can cause functional alterations in membrane ion channelsas well as alterations in ion channel expression. These changes furtherperpetuate atrial fibrillation.

Radiofrequency (RF) ablation is an effective therapy for treating atrialand ventricular rhythm disturbances. Nearly 100,000 RF ablationprocedures are performed annually in the United States to treat cardiacarrhythmias. RF ablation targets the key elements of reentrant pathwaysand/or abnormal ectopic loci without damaging significant amounts ofadjacent healthy myocardium and coronary vessels. Ablations are alsodone with cryo-ablation and laser guided ablation systems.

To perform an RF ablation procedure, a catheter is threaded into theheart and the tip is guided into the atria. A transseptal puncture ismade to allow cross-over from the right atrium into the left atriumwhere the crux of the ablation is performed. The catheter then emits apulse of high-energy RF electricity that damages atrial tissues andforms scar tissue that blocks abnormal signals. The most common RFablation treatment of atrial fibrillation consists of placing ablationlesions in a circular fashion around the ostium of each pulmonary vein.The lesions electrically isolate the pulmonary veins to block focaltriggers from entering the left atrium. RF lesions can also be placedepicardially during minimally invasive or open heart surgery.

The extent of RF ablation lesions is not simply a function of deliveredRF energy, but depends on many factors, including the contact betweenthe catheter tip and the tissue, the thickness of the myocardium, thedegree of blood flow, and the presence of fat. Currently we usesurrogates to determine anatomy known as 3D mapping systems (CARTO andNAVEX), surrogates can be off by 1 or 2 cm. Current electro-anatomicalmapping systems map mainly the physical location of the catheter tip butnot the extent of cell injury caused by the ablations. Therefore, as oftoday, RF ablation lesions are created with no information regarding thephysiological condition of the affected tissue. This is problematicconsidering that gaps of excitable tissue between ablation lesions aredirectly related to arrhythmia recurrences. Monitoring tissue injuryproduced by ablation in real time remains a major limitation of currentablation approaches.

To resolve the problem of incomplete lesions, two main strategies havebeen proposed. The first is to improve ablation devices, which includesthe development of multi-polar and linear catheters, balloon-basedtechnologies using lasers and high-intensity focused ultrasound, as wellas pressure-sensor equipped RF catheters.

The second strategy is to visualize RF ablation lesions during theablation procedure. Such visualization can be based upon acute changesin the chemical and/or physical properties of the damaged tissue.Specifically, the current visualization proposals require the use of adye and include magnetic resonance imaging (MRI), coherence tomography(CT) and spectroscopy.

All these strategies use surrogates to predict the areas of the gaps andnone has a real time direct visualization technique as we have designed.Despite all the current technology, pulmonary vein reconnections occurin 94% of patients after the first procedure. Atrial fibrillationrecurrences after ablation procedures are 80-90% of the time due topulmonary vein reconnection at the sites of gaps.

SUMMARY

Systems and methods for visualizing ablated tissue are disclosed herein.

According to some aspects illustrated herein, there is provided a systemfor imaging tissue that includes a catheter having a distal end and aproximal end; an inflatable balloon disposed about the distal end of thecatheter; and an optical housing extending from the distal end of thecatheter into the balloon, the optical housing being configured toposition inside the balloon a light source for illuminating a tissueoutside the balloon and a camera for imaging the illuminated tissue.

According to some aspects illustrated herein, there is provided a systemfor imaging tissue that includes a catheter having a distal end and aproximal end; an inflatable balloon disposed about the distal end of thecatheter; and an optical housing extending from the distal end of thecatheter into the balloon; a light source inside the balloon, the lightsource being supported by the optical housing and configured to excitenative reduced form of nicotinamide adenine dinucleotide or nicotinamideadenine dinucleotide hydrogen (NADH) in a tissue; and a camera insidethe balloon, the camera being supported by the optical housing andconfigured to image the tissue illuminated by the light source.

According to some aspects illustrated herein, there is provided a systemfor imaging tissue that includes a catheter having a distal end and aproximal end; an irrigation port to displace blood with a fluid aboutthe distal end of the catheter; and an optical housing extending fromthe distal end of the catheter, the optical housing being configured tosupport a light emitting diode light source for illuminating tissue anda visualization device including a plurality of image sensors thatconvert an optical image into an electronic signal for imaging theilluminated tissue.

According to some aspects illustrated herein, there is provided a systemfor imaging tissue that includes a sheath for infusing a fluid capableof displacing blood and transmitting light; a catheter disposed withinthe sheath, the catheter having a distal end and a proximal end; anoptical housing extending from the distal end of the catheter, theoptical housing being configured to support a light emitting diode lightsource for illuminating tissue and a visualization device including aplurality of image sensors that converts an optical image into anelectronic signal for imaging the illuminated tissue.

According to some aspects illustrated herein, there is provided a methodfor imaging tissue that includes advancing to a tissue a cathetercomprising an inflatable balloon disposed about the distal end of thecatheter and an optical housing extending from the distal end of thecatheter into the balloon to position a light source and a camera insidethe balloon; ablating the tissue; illuminating with the light source anarea of tissue including tissue treated by ablation and surroundingtissue to excite NADH in the area of tissue; imaging with an imagingdevice the area of tissue to detect NADH fluorescence of the area oftissue; and producing a display of the imaged, illuminated tissue, thedisplay illustrating ablated tissue as having less fluorescence thannon-ablated tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The presently disclosed embodiments will be further explained withreference to the attached drawings, wherein like structures are referredto by like numerals throughout the several views. The drawings shown arenot necessarily to scale, with emphasis instead generally being placedupon illustrating the principles of the presently disclosed embodiments.

FIG. 1A is a block diagram of an exemplary system in accordance with thepresent disclosure;

FIG. 1B illustrates an embodiment of a catheter for use in an exemplarysystem in accordance with the present disclosure;

FIG. 1C illustrates a distal end of an embodiment of a catheter for usein an exemplary system in accordance with the present disclosure;

FIG. 1D illustrates a proximal end of an embodiment of a catheter foruse in an exemplary system in accordance with the present disclosure;

FIG. 2A is a block diagram of an exemplary system in accordance with thepresent disclosure;

FIG. 2B illustrates an embodiment filter box for use in connection withthe exemplary system shown in FIG. 2A;

FIG. 3 is a flow diagram of an exemplary method in accordance with thepresent disclosure;

FIG. 4A illustrates a RF ablation probe in the position to deliver alesion onto the epicardial surface;

FIG. 4B illustrates the visual appearance of a typical lesion after astandard RF ablation protocol performed in a blood-free rat heart;

FIG. 4C illustrates the appearance of two distinct RF ablation lesionsin a blood-free heart, as revealed by fNADH imaging;

FIG. 4D illustrates the appearance of the same two RF ablation lesionsafter TTC staining with vital TTC dye (white tissue—necrotic,red—viable);

FIG. 4E illustrates transverse slicing through TTC-stained heart showingdepth of two lesions placed on opposite epicardial surfaces using twodifferent power settings;

FIG. 5A illustrates lesion stability over time as seen onfNADH-sensitive channel;

FIG. 5B illustrates an image of radiofrequency ablation lesion on theepicardial surface of an excised rat heart 2 months after survivalsurgery as seen on fNADH-sensitive channel;

FIG. 6A, FIG. 6B and FIG. 6C illustrate comparison between the sizes ofthe RF lesions as they are seen on fNADH-sensitive channel and after TTCstaining;

FIG. 7A, FIG. 7B and FIG. 7C illustrate occurrence of reentry betweentwo RF lesions based on data from dual imaging of epicardial electricalactivity using voltage sensitive dye and fNADH. Reentry formation occursas electrical waves propagate through narrow isthmus between two RFlesions;

FIG. 8A, FIG. 8B, FIG. 8C and FIG. 8D illustrate profiles of fNADH andelectrical activity across the isthmus between two RF lesions;

FIG. 9A, FIG. 9B, FIG. 9C and FIG. 9D illustrate RH237 retention withinthe ablation areas;

FIG. 10A, FIG. 10B, FIG. 10C and FIG. 10D illustrate RH237 retentionafter RF ablation procedure as it compares to NADH fluorescence. FIG.10A is a schematic representation of lesion formation by RF catheter.FIGS. 10B and 10C show RF ablations done in rat hearts, and FIG. 10Dshows RF ablations done in a rabbit heart;

FIGS. 11A-11D illustrate visualization of RF ablation lesions inblood-perfused open-chest animals. As shown in FIG. 11D the ablatedlesion is identified by lack of fluorescence which gives the tissue adark appearance (center portion of the figure) whereas the ischemic orinjured tissue becomes brighter as illustrated by the halo typeappearance;

FIG. 12 is an image of an ablation lesion on the endocardial surface ofblood perfused canine left atrial tissue near pulmonary veins;

FIG. 13 is an image of an ablation lesion on epicardial surface ofblood-free rat hart after cryo-ablation;

FIG. 14 illustrates fNADH lesion in rat blood-perfused liver that hasbeen acutely ablated using radiofrequency ablation; and

FIG. 15 is a 2D image on the right of a standard catheter andreconstruction into 3D integrated into 3D mapping system. A computersystem and program can be used to convert the acquired 2D image of NADHfluorescence into a 3D image superimposed on the atrial anatomy asdisplayed.

FIG. 16 is a view of an embodiment of the balloon catheter assembly ofthe present disclosure.

FIG. 17 is a view of an embodiment of the balloon catheter assembly ofthe present disclosure with balloon hidden.

FIG. 18 is a view of an embodiment optical housing inserted into anembodiment catheter of the present disclosure.

FIG. 19, FIG. 20 and FIG. 21 illustrate various non-limiting embodimentsof an optical housing of the present disclosure.

While the above-identified drawings set forth presently disclosedembodiments, other embodiments are also contemplated, as noted in thediscussion. This disclosure presents illustrative embodiments by way ofrepresentation and not limitation. Numerous other modifications andembodiments can be devised by those skilled in the art which fall withinthe scope and spirit of the principles of the presently disclosedembodiments.

DETAILED DESCRIPTION

Exemplary embodiments of the present disclosure are directed to systemsand methods of visualizing RF ablation lesions during an ablationprocedure. Systems and methods for treating Atrial Fibrillation (AF) arealso provided.

Systems, catheter and methods for treating Atrial Fibrillation (AF) areprovided. The fluorescence of endogenous NADH (fNADH) in heart tissue isimaged to identify ablated and unablated areas using a balloon guidedcatheter equipped with UV illumination source and UV capable fiber, afluorescence capable camera or imaging bundle and optical band passfilter to detect NADH fluorescence. Gaps between ablated areas can beidentified using the fNADH imaging and the gaps can then be ablated. Theimaging can be performed during the ablation procedure and does notrequire additional chemicals, such as contrast agents, tracers or dyes.

In some embodiments, the systems of the present disclosure can beutilized to illuminate tissue using ultra-violet light and thefluorescence of endogenous NADH (fNADH) can be imaged to identifyablated and unablated areas. The provision of ultra-violet light andimaging of the fNADH of the tissue can be achieved using, for example, adual UV excitation/emission fiber-optic waveguide located at the tip ofthe catheter. The methods and systems of the present disclosure do notrequire the addition of dyes and stains. Moreover, the methods andsystems of the present disclosure allow imaging during the ablationprocedure so as to not require an additional invasive ablation procedurefollowing the initial procedure. Utilizing the methods and systems ofthe present disclosure results in having a completely dark area at thesites of complete ablation due to lack of fluorescence which may enhancethe ability to detect the ablated areas by providing marked contrast tothe healthy tissue and even more contrast at the border zone betweenablated and healthy tissue. This border area is the edematous andischemic tissue in which NADH fluorescence becomes bright white uponimaging. The border zone creates a halo appearance around the ablatedcentral tissue.

In accordance with exemplary embodiments of the present disclosure,ablated tissue and tissue surrounding the ablated tissue is imaged usingthe fluorescence of endogenous NADH (fNADH) using low-intensityultraviolet light illumination. NADH is a coenzyme that is presentwithin intact cells and is particularly abundant in cardiac musclecells. Once NADH is released from mitochondria of damaged cells and/orconverted to its oxidized NAD+ form, cardiomyocyte fNADH markedlydeclines. This reveals the ablation-induced muscle injury to highlightgaps that indicate incomplete epicardial lesions.

Ablations are currently performed without meaningful real-timeinformation regarding the physiology of the ablated tissue. Electricalisolation of focal sources is the only indicator of ablation efficiency.There are two main limitations of this approach. The first is that theextent of the lesions cannot be measured during the procedure. Thesecond is that the specific cause of electrical isolation cannot bedetermined. For example, electrical isolation may result from cardiacmuscle damage, but also from functional changes in reversibly injuredcells, as well as by temporary edema. In the case of edema, it maysubside after a few weeks, potentially restoring abnormal electricalconduction. The fNADH imaging of the present disclosure revealsirreversible cardiac muscle injury without contrast agents, tracers ordyes. Lesions examined via fNADH imaging are seen immediately afterdelivering RF energy and they are stable for several hours. Therefore,visualization can be done concordantly with ablation or after multiplelesions have been placed.

There is no contradiction between the increase in NADH fluorescenceduring ischemic injury used in the present disclosure as opposed to adecrease upon thermal damage due to the following reasons. About thirtypercent of cardiomyocyte volume is comprised of mitochondria, whichcontain a large amount of NADH. Accordingly, changes in the level offNADH from myocytes can be measured with relative ease. When thesarcolemma and mitochondrial membranes are disrupted by heat, NADH islost and fNADH levels immediately fall. During hypoxia and/or ischemia,cellular integrity is preserved but oxygen availability is reduced.Oxygen serves as a final electron acceptor in the mitochondrial electronchain and its decline leads to NADH accumulation. Thus, ischemia causesan increase in fNADH in a time dependent manner. For example, ifcoronary perfusion is temporarily disrupted during ablation, patches ofischemic or injured tissue with elevated fNADH levels may be observedadjacent to the darker circular fNADH lesions after ablation, which canbe seen in FIG. 4C.

Monitoring endogenous fNADH can be done without additional tracers orcontrast agents. Since changes in fluorescence reflect acute biochemicalchanges, lesions are seen almost immediately. Although imagingmodalities such as MRI, C-arm CT, and contrast echocardiography areexcellent tools in detecting parameters resulting from heat inducedbiophysical changes, contrast agents are required to visualize changesin real time. Additionally, while MRI and C-arm CT provide high spatialresolution, it could take up to 30 minutes to visualize cell necrosis.Echocardiography is faster but suffers from low spatial resolution andlimited field of view. Other modalities based on physical tissue changesincluding alteration in tissue elasticity, impedance, or absorption havealso been explored. While such strategies provide real-time feedback andmay predict lesion size and depth, they also require significant dataprocessing and don't provide direct visualization of the ablated region.It should, however, be noted that these well-known imaging methods maybe used in combination with the methods of the present disclosure.

Today a majority of ablation procedures are endocardial butapproximately 10 to 20% could be applied to the epicardium. Epicardialsubstrates are frequently observed for VT, including >20% of postinfarctVTs, and >30% of VTs from nonischemic cardiomyopathy, particularly forChagas disease. Ablation of these epicardial substrates may use apercutaneous approach that involves the subxiphoid placement of sheathsinto an intact, closed pericardial space. fNADH imaging is particularlyuseful for these procedures. Conventional endoscopes equipped withUV-compatible optics and light sensitive image capture devices would besuitable for this purpose. Air insufflation through the endoscope couldbe used to expand the pericardial space for adequate visualization ofablation sites. In a clinical setting, insufflation with carbon dioxiderather than air would likely reduce the risk of air embolization. fNADHimaging might also be used for endocardial procedures if blood isdisplaced using inflatable balloons in front of an endoscope.

The systems and methods of the present disclosure enable the user tomonitor myocardial damage while performing an ablation. By doing so,clinical cardiac electrophysiologists may be able to shorten the timeand improve the efficiency of ablation, minimize unnecessary tissueinjury that may cause post ablation complications, and decreasepost-ablation recurrence of arrhythmias and the need for follow-upablations. fNADH imaging may also be useful for mechanistic studies oftissue injury near the ablation sites and for assessment of drugs thatmay alter electrical propagation between inter-lesion gaps.

The use of fNADH imaging allows visualizing of ablation lesions and gapsbetween lesions in both blood-free and blood-perfused rat and rabbithearts. Optical action potentials and the endogenous fluorescence ofNADH can be imaged to study changes in electrical activity and tissueviability around ablation lesions. The fNADH imaging can be accomplishedduring ablation procedures using a dual UV excitation/emissionfiber-optic waveguide located at the tip of a catheter. Such a waveguidesystem could interface with a 3D mapping system to provide a detailedmap of cardiac muscle viability near the catheter.

FIG. 1A is a block diagram of an exemplary system in accordance with thepresent disclosure. The system includes an inflatable balloon catheter105 coupled to external equipment 125. In some embodiments, the catheter105 includes an ablation device 110, illumination device 115 and animaging device 120. In some embodiments, the illumination device 115 andan imaging device 120 may utilize a fiber-optic waveguide to pass thelight to and from the treated tissue.

In some embodiments, the methods and systems of the present disclosuremay be used in connection with ablation procedures to monitor in realtime when the complete ablation of desired tissue has been achieved.Ablation is a process that uses energy, heat or extreme cold (cryo) todestroy or damage tissue (ablation). For example, RF ablation relies onheat generated from the high frequency alternating current to ablatetissue. Cryoablation is used in a variety of clinical applications usinghollow tubes or needles (cryoprobes) through which cooled, thermallyconductive, fluids are circulated, to destroy the tissue by freezing thetissue. The systems and methods of the present disclosure may beutilized in connection with various types of tissue ablation, including,but not limited to, RF ablation, cryoablation, acoustic energy ablation,electromagnetic energy ablation, microwave energy ablation, ultrasoundablation, chemical ablation, laser ablation, thermal ablation,electrical ablation or other types of thermal or non-thermal energyablations. To that end, in some embodiments, the ablation device 110 maybe advanced to a tissue in need of ablation to ablate the tissue. Insome embodiments, the ablation device 110 has an energy source selectedfrom the group consisting of radiofrequency energy, microwave energy,electrical energy, electromagnetic energy, cryoenergy, laser energy,ultrasound energy, acoustic energy, chemical energy, and thermal energy.

The external equipment 125 includes a light source 130, which providesultra-violet light to illumination device 115, a camera 135 and adisplay 140. In some embodiments, the camera 135 can be a CCD camerathat has a high quantum efficiency for wavelengths corresponding to NADHfluorescence (i.e., 80% quantum efficiency at 460 nm), such as an AndorIxon DV860 camera. In some embodiments, the camera 135 may be equippedwith a 460/25 nm filter 135 (i.e., a filter to pass ultra-violet lightwhile blocking light outside of the ultra-violet spectrum).

In reference to FIG. 1B, in some embodiments, the catheter 105 is amulti-lumen catheter having a proximal end 220 and a distal end 221. Thecatheter 105 includes a balloon 222 disposed about the distal end 221 ofthe catheter 105. The balloon 222 may be made of a UV transparentmaterial, such as, for example, a UV transparent fluoropolymer. In someembodiments, the balloon 222 may have a thickness of 50 μm andrefractive index of 1.31. The balloon 222 may be either a complaintballoon or a non-complaint balloon.

The balloon 222 may be round, flat, cylindrical, oval, rectangular oranother shape depending on the anatomy to be treated using the catheter105. The balloon 222 may displace blood at the site of fluorescenceimaging in order to afford an optically uncluttered view. Since bloodpossesses fluorescent properties mostly due to the hemoglobin, imagingthrough this medium would saturate the emission pathway. The balloon maybe inflated with a gas or a liquid. For example, carbon dioxide, whichhas a low refractive index of about 1.00045, may be used to inflate theballoon. Also, in the event of a balloon breach in vivo, CO₂ exposure inthe short term would not pose any immediate mortal danger due to theabundant partial pressure of N₂ gas. Suitable liquids include, but arenot limited to, water, saline, blood or another similar liquid. Thecatheter 105 may include an inflation/deflation lumen 225 for inflatingand deflating the balloon 222. Two separate lumens may be provided insome embodiments for inflating and deflating the balloon 222.

In addition to the inflation/deflation lumen 225, the catheter 105 mayfurther include an ablation lumen 223 for advancing an ablation device110, an imaging lumen 224 for advancing an imaging device 120, and anillumination lumen 226 for advancing an illumination device 115. Itshould of course be understood that the catheter 105 may includeadditional lumens or some lumens may serve multiple functions. Forexample, in some embodiments, a single fiber optic bundle may beemployed to pass the light from a light source 130 to the tissue toilluminate the tissue and to pass the light reflected by the tissue to acamera 135.

In reference to FIG. 1C, an embodiment of the distal tip 221 of thecatheter 105 without the balloon 222 is illustrated. The ablation lumen223 allows an ablation device 110 to be passed to or past the distal end221 of the catheter 105 for ablation of desired tissue. Theinflation/deflation lumen 225 enables the user to inflate and deflatethe balloon 222 to aid in fluorescence imaging. The imaging lumen 224allows an imaging device 120 to be advanced into the balloon for imagingthe ablated tissue, which can be illuminated by an illumination device105 advanced through the illumination lumen 226. It should of course beunderstood that, to the extent desired, the position of various lumens223-226 in relation to one another may be varied.

In reference to FIG. 1D, an embodiment of the proximal tip 220 isillustrated. In some embodiments, an ablation port 233 in communicationwith the ablation lumen 223 may be provided for introducing an ablationdevice 110 into the catheter 105. Another port 235 may be provided incommunication with the inflation lumen 225 a and deflation lumen 225 bfor operating the balloon 222. In some embodiments, the proximal end 220includes an outlet 237 in communication with the imaging lumen 224 andillumination lumen 226 to introduce an imaging device 120 and anillumination device 110 into the catheter 105. The catheter 105 may alsobe provided with a connector 240 for connecting the catheter 105 to oneor more external equipment 125.

Referring back to FIG. 1A, the external equipment 125 may include acamera 135. In some embodiments, the camera 135 may be a CCD(charge-coupled device) camera. In some embodiments, the camera 135 maybe selected so it is capable of collecting as many photons as possibleand that contributes minimal noise to the image. Usually forfluorescence imaging of live cells, CCD cameras should have a quantumefficiency at about 460 nm of at least between 50-70%, indicating that30-50% of photons will be disregarded. In some embodiments, the camera135 has quantum efficiency at 460 of about 90%. The camera 135 may havea sample rate of 80 KHz. In some embodiments, the camera 135 may have areadout noise of 8 e⁻ (electrons) or less. In some embodiments, thecamera 135 has a minimum readout noise of 3e⁻.

The external equipment 125 may further include a light source 130, suchas a UV LED emitter. The light source is utilized to illuminate tissuevia an imaging device 120, which may comprise a fiber optic light guideand may be advanced through the imaging lumen 224 to the distal tip 221of the catheter 105 to capture tissue images. In some embodiments, thefiber optic light guide can act as an illumination device 115 to passthe light at excitation wavelength from a light source 130 to the tissuefor illuminating tissue to be visualized. The fiber optic light guidecan also act to pass the light reflected by the tissue back to thecamera 135. In some embodiments, separate fiber optics networks can beused for illumination and imaging that is, in some embodiments anillumination device 115 may be independent of the imaging device 120. Insome embodiments, a fiberscope can be used as an imaging device,illumination device, or both.

Once the images of illuminated tissue are captured by the CCD, theseimages can be transmitted to a display 140 to be displayed to the userin real time. The images can be analyzed by using software to obtainreal-time details (e.g. intensity or radiated energy in a specific siteof the image) to help the user to determine whether further interventionis necessary or desirable.

In reference to FIG. 2A, in some embodiments, the system of the presentdisclosure may include a filter box 145 positioned between the cathetersystem 105 and the external equipment 125, such as the camera 135 andlight source 130. The filter box 145 may include a dichroic mirror 146for reflecting light from the light source 130 to be propagated by theillumination device 115. The dichroic mirror 146 may be placed at a 45°incidence angle to light, creating a stop band of reflected light and apass band of transmitted light. Light from the light source 130 isreflected by 90° in the direction of the specimen. Concurrently, in thesame orientation, light emanating from the specimen is passed throughthe mirror. In some embodiments, a longpass dichroic mirror with acutoff (50%) wavelength of 425 nm may be used as it has an approximatereflection band of more than 80% between 355 nm and 410 nm and atransmission band of more than 90% between 440 nm and 700 nm. Of courseit should be understood that other optical devices may be used to passlight to and from the tissue to be visualized.

The filter box 145 may also include an emission filter 147 to filter outlight that may contribute as some sort of noise or unwanted feature. Insome embodiments, based on the NADH fluorescence, the filter 147 may bea center wavelength of 460 nm with a 50-nm bandwidth (i.e. 460±25 mm)The filter box 145 may further include an excitation filter forselection of the excitation wavelength of light from the light source130.

In reference to FIG. 2B, an embodiment filter box 145 includes a cameraport 400 with an emission filter 401 held in a filter holder 402positioned in front of the camera port 400. The filter box 145 furtherincludes an excitation filter 403 held in a filter holder 404, which maybe positioned either at a light source port or a catheter port. Theexcitation filter 403 is positioned at a catheter port 405. A dichroicmirror 405 is inserted into a mirror slot 406 and is positioned at abouta 45 degree angle to a port for attaching the light source 130 to thefilter box 145.

In reference to FIG. 3, operation of the systems of the presentdisclosure is illustrated. Initially, catheter 105 is inserted into thearea affected by the atrial fibrillation, such as the pulmonaryvein/left atrial junction (step 150). Blood is removed from the visualfield. For atrial fibrillation ablation a transparent balloonsurrounding the fiber optic waveguide would be used to displace theblood at the pulmonary vein/left atrial junction. The affected area isilluminated by ultra-violet light from source 130 and illuminationdevice 115 (step 155) and tissue in the illuminated area is ablatedusing ablation device 110 (step 160). Either point-to-point RF ablationor cryoablation or laser or other known ablation procedures may beemployed using the systems of the present disclosure. Ablation proceedsby threading the tip through the central lumen of the catheter. Afterthe procedure, the ablation tip may be retracted.

The illuminated area is imaged by the combination of imaging device 120and camera 135 (step 165). The methods of the present disclosure rely onimaging of the fluorescence emission of NADH, which is a reduced form ofnicotinamide adenine dinucleotide (NAD+). NAD+ is a coenzyme that playsimportant roles in the aerobic metabolic redox reactions of all livingcells. It acts as an oxidizing agent by accepting electrons from citricacid cycle (tricarboxylic acid cycle), which occurs in themitochondrion. By this process, NAD+ is thus reduced to NADH. NADH andNAD+ are most abundant in the respiratory unit of the cell, themitochondria, but are also present in the cytoplasm. NADH is an electronand proton donor in mitochondria to regulate the metabolism of the celland to participate in many biological processes including DNA repair andtranscription.

By measuring the UV-induced fluorescence of tissue, it is possible tolearn about the biochemical state of the tissue. NADH fluorescence hasbeen studied for its use in monitoring cell metabolic activities andcell death. Several studies in vitro and in vivo investigated thepotential of using NADH fluorescence intensity as an intrinsic biomarkerof cell death (either apoptosis or necrosis) monitoring. Once NADH isreleased from the mitochondria of damaged cells or converted to itsoxidized form (NAD+), its fluorescence markedly declines, thus making itvery useful in the differentiation of a healthy tissue from a damagedtissue. NADH can accumulate in the cell during ischemic states whenoxygen is not available, increasing the fluorescent intensity. However,NADH presence disappears all together in the case of a dead cell. Thefollowing table summarizes the different states of relative intensitydue to NADH fluorescence:

Relative Changes of Auto- Cellular State NADH Presence fluorescenseintensity Metabolically Active Normal Baseline Metabolically Active butIncreased to Increased Impaired (Ischemia) Hypoxia MetabolicallyInactive None Full Attenuation (Necrotic)

While both NAD+ and NADH absorb UV light quite readily, NADH isautofluorescent in response to UV excitation whereas NAD+ is not. NADHhas a UV excitation peak of about 350-360 nm and an emission peak ofabout 460 nm. In some embodiments, the methods of the present disclosuremay employ excitation wavelengths between about 335 to about 380 nm.With the proper instrumentation, it is thus possible to image theemission wavelengths as a real-time measure of hypoxia as well asnecrotic tissue within a region of interest. Furthermore, a relativemetric can be realized with a grayscale rendering proportionate to NADHfluorescence.

Under hypoxic conditions, the oxygen levels decline. The subsequentfNADH emission signal may increase in intensity indicating an excess ofmitochondrial NADH. If hypoxia is left unchecked, full attenuation ofthe signal will ultimately occur as the affected cells along with theirmitochondria die. High contrast in NADH levels may be used to identifythe perimeter of terminally damaged ablated tissue.

To initiate fluorescence imaging, the operator may deploy the balloon,which is installed around the distal portion of the catheter. Next, NADHis excited by the UV light from the light source 130. In someembodiments with a filter box, first the excitation light from the lightsource hits the dichromatic mirror (or dichroic beam splitter)positioned within the filter box 145. Then the excitation light isreflected by the dichromatic mirror toward the specimen via the fiberoptic. In some embodiments, the mirror may be positioned at a 45° anglerelative to the excitation light and the excitation light may bereflected 90°. In some embodiments, the methods of the presentdisclosure may employ excitation wavelengths between about 335 to about380 nm.

NADH in the tissue specimen absorbs the excitation wavelengths of lightand emit longer wavelengths of light. The emission light may becollected and passed back through the dichromatic mirror 146. Thismirror 146 may therefore be designed to reflect the excitationwavelengths, but transmit the emission wavelengths. The reflection ofthe excitation wavelengths is not 100%, so a small amount of this lightpasses through the dichromatic mirror 146. Likewise, additional lightwith a different wavelength could pass through, and thus an emissionfilter may be employed in connection with the camera 135. The emissionfilter may be selected for the emission wavelengths of light expectedfrom the fluorophore such as NADH.

Once the light is filtered, the light may be collected by the camera135, and a display of the imaged illuminated area is produced on display140 (step 170), which is used to identify the ablated and unablatedtissue in the imaged area using NADH florescence (step 175). The processthen repeats by returning to the ablation step, if necessary to ablateadditional tissue. It should be recognized that although FIG. 3illustrates the steps being performed sequentially, many of the stepswill be performed simultaneously or nearly simultaneously. Thus, forexample, the ablation, imaging and display can occur at the same time,and the identification of the ablated and unablated tissue can occurwhile ablating the tissue.

The methods, systems and devices disclosed herein can be used for avariety of therapeutic procedures. Exemplary procedures in which themethods, systems and devices disclosed herein can be utilized include,but not limited to, for diagnostic and therapeutic procedures in theheart, for treating arrhythmias, such as, for example, supraventriculararrhythmias and ventricular arrhythmias, for treating atrialfibrillation, and pulmonary vein mapping and ablation. The ablatedtissue may be cardiac muscle, but the methods disclosed herein shouldhave the same effect on skeletal muscle, liver, kidney, and othertissues with significant presence of NADH-rich mitochondria.

In reference to FIG. 16, a catheter 1601 for use in connection withsystems and methods of the present disclosure includes one or morelumens extending therethrough and an expandable balloon 1603 disposedabout the distal end of the catheter 1601. In some embodiments, theballoon 1603 may be attached at its proximal tip 1604 to the distal endof the body of the catheter 1601 and attached at its distal tip 1605 toa catheter tip 1606, which may be connected to the catheter 1601 by atube or lumen as described below. The balloon 1603 may be made from anoptically transparent material and may be used to move blood out of theway for the optical components during fluorescence imaging. The balloon1603 can be made of many different materials and shapes that would bestconform to various anatomic structures. The balloons may be constructedof a soft material, such as silicone, and be compliant to the anatomy.Alternatively, the balloon may be constructed of a stronger material,such as polyurethane, and be less compliant. As illustrated in FIG. 16,the balloon 1603 may have a conical shape designed for insertion intothe ostium of the pulmonary veins. Other shapes of a more circularnature may be better suited for visualizing other cardiac anatomicalsights for ablation therapy, including, by way of a non-limitingexample, accessory pathways, ventricular wall sites, atrial wall sights,or atrio-ventricular nodal sights.

The catheter 1601 may be utilized for tissue ablation, including, butnot limited to, RF ablation, cryoablation, acoustic energy ablation,electromagnetic energy ablation, microwave energy ablation, ultrasoundablation, chemical ablation, laser ablation, thermal ablation,electrical ablation or other types of thermal or non-thermal energyablations. To that end, in some embodiments, the catheter 1601 may beadvanced to a tissue in need of ablation and an ablation member capableof performing one more ablation methods can be passed through thecatheter 1601 to ablate the tissue. In some embodiments, the ablationmember has an energy source selected from the group consisting ofradiofrequency energy, microwave energy, electrical energy,electromagnetic energy, cryoenergy, laser energy, ultrasound energy,acoustic energy, chemical energy, and thermal energy.

In some embodiments, the catheter tip 1606 may be configured to act asan electrode either for diagnostic purposes, such as electrogramsensing, or for therapeutic purposes, such as for emitting ablationenergy. In some embodiments where ablation energy is required of thecatheter, the tip 1606 of the catheter 1601 could serve as an ablationelectrode or ablation element. In the embodiments where RF energy isimplemented, the wiring to couple the tip to the RF energy source(external to the catheter) can be passed through a lumen of the catheter1601. The tip 1606 may include a port 1607 in communication with the oneor more lumens of the catheter 1601. In this manner, a guide wire orother surgical instruments, such as, for example, an RF electrode, maybe advanced out of the catheter 1601 past the tip 1606. The tip 1606 canbe made of any biocompatible material. In some embodiments, if the tipis configured to act as an electrode, the tip 1606 can be made of metal,including, but not limited to, platinum, platinized iridium, stainlesssteel, or titanium. The tip 1606 may also be made of a biocompatibleplastic, including, but not limited to, silicone, peek, polyurethane.

In reference to FIG. 17, in some embodiments, the catheter tip 1606 maybe connected to the main body of the catheter 1601 by a guide wire tube1700 extend past distal tip of the main body of the catheter 1601. Theguide wire tube 1700 may include one or more lumens in communicationwith one or more lumens of the catheter 1601 for advancing a guide wire,ablation member or other surgical instruments past the distal tip of thecatheter 1601. The inner lumens of the guide wire tube 1700 may also bein communication with the port 1607 of the catheter tip 1606 foradvancing surgical instruments through the guide wire tube 1700 to orpast the catheter tip 1606.

In some embodiments, the guide wire tube 1700 may act to providestructural support to the balloon 1603, especially when the balloon 1603is in a deflated state during the advancement of the catheter 1601 tothe treatment site. In some embodiments, the guide wire tube 1700 may besemi-rigid to provide structural support to the balloon 1603. In someembodiments, the guide wire tube 1700 may be an integral lumen of thecatheter 1601. In some embodiments, the guide wire tube 1700 is separatefrom the catheter 1601 and may be removable inserted into the distal tipof the catheter 1601. In some embodiments, the guide wire tube 1700 maybe slidable disposed within the catheter 1601, so that the guide wiretube 1700 may be moved in relation to the catheter 1601 to adjust theshape of the balloon 1603 to aid in advancement or withdrawal of thecatheter 1601 from the patient's body. For example, the guide wire tube1700 may be advanced to stretch a collapsed balloon for easierwithdrawal out of the patient's body. In such a state, the balloon wouldbe more behaved and less likely to get caught on an introducer sheathwhen being removed. The guide wire tube may be made of any material. Insome embodiments, the guide wire tube 1700 may be made from a shapememory material, such as Nitinol.

In reference to FIG. 17 in combination with FIG. 16, the catheter 1601may include a neck down surface 1701 where the proximal end 1604 of theballoon 1603 may be attached to the catheter 1601 without increasing theouter diameter of the combined device.

In reference to FIG. 18, an optical housing 1803 may be disposed at thedistal end of the catheter 1601 for positioning optical elements, suchas a camera 1804 and a light source 1805, inside the balloon 1603. Theoptical housing 1803 enables positioning of the camera 1804 and lightsource 1805 within the balloon, thus eliminating the need for anexternal light source. Moreover, by putting the light sources within theballoon, wider angles of illumination may be achieved than when using afiber bundle. As is shown in FIG. 18, the optical housing 1803 canextend from the catheter into the balloon such that the light source andthe camera are completely contained within the balloon to ensure thatthe catheter does not interfere with the field of view of the lightsource or the camera. As shown in FIG. 18, that the light source and thecamera are internal to the balloon and do not extend outside theballoon. In some embodiments, the housing 1803 may position the opticalelements in a fixed relation to one another. In some embodiments, thecamera 1804 and the light source 1805 are flush with each other so thatneither component “blocks” the function of the other. Being flushassures that the camera 1804 will not block illumination nor will thelight source 1805 show up in the camera image. In some embodiments, theposition of the components may altered to avoid interference of oneoptical component with the other one.

The camera 1804 may be any image sensor that can convert an opticalimage into an electronic signal. In some embodiments, the camera is aminiature CMOS image sensor with a lens and with or without a filter tochoose a specific wavelength or set of wavelengths to record. In someembodiments, the camera is a CCD camera or other image sensors that canconvert an optical image into an electronic signal. The camera maytransmit its signal via wires to external image processor and videoterminal for the physician to see. In some embodiments, the camera mayhave wireless communication capabilities for communication with externaldevices. The light source 1805 may be a light emitting diode (LED) ofsuitable wavelength. In some embodiments, the LED will have a wavelengthin the UV range to cause the NADH fluorescence. In some embodiments,different wavelengths including white light for multicolor illuminationare possible by choosing the LED of the appropriate wavelength. By wayof a non-limiting example, suitable LEDs for UV applications wouldinclude those with wavelengths of 300 nm to 400 nm, while suitable LEDsfor visible or white light applications would include those with colortemperature ranges from 2000K to 8000K.

As shown in FIG. 18, the housing 1803 may be inserted into the distalend of the catheter 1601. In some embodiments, the outer diameter of thehousing 1803 may be smaller than the inner diameter of the catheter 1601such that a gap 1802 may be formed between the inner wall of thecatheter 1601 and the housing 1803. In some embodiments, the balloon1603 may be deflated or inflated through the gap 1802. It should ofcourse be understood that a separate lumen may be provided for operatingthe balloon 1603.

In some embodiments, because the outer diameter of the optical housing1803 is smaller than the inner diameter of the catheter 1601, thehousing 1803 may be moveable in relation to the catheter 1601. In someembodiments, the housing 1803 may be freely rotated in relation to thecatheter 1601 and, thus the balloon 1603. In some embodiments, theoptical housing 1803 may be translated longitudinally in relation to theballoon catheter 1601 to obtain a desired view point for the camera orillumination position for the light source. A lock may be provided tolock the optical housing 1803 in a desired position.

FIG. 19 is a view of the housing 1803 outside the catheter 1601, showinga wire bundle 1901 of the camera 1804 and a wire bundle 1902 for thelight source 1805. These wire bundles may run the entire length of thecatheter back to the handle (not shown) where they can make electricalconnections to the remainder of the imaging system, such as a powersource or a display. It should be noted however that, in someembodiments, the camera may have wireless communication capabilities forwireless communication with external devices

The housing 1803 also includes a channel 1904 for accepting a guide wiretube 1700 to facilitate communication between the guide wire tube 1700and the catheter 1601.

The catheters of the present disclosure may be used inminimally-invasive procedures as well as in conventional surgicalprocedures, i.e. open procedures. In some embodiments, the catheters ofthe present disclosure may be configured for endovascular approach. Insome embodiments, the catheters of the present disclosure may beconfigured for non-endovascular approach. In some embodiments, thesystems of the present disclosure may be surgical systems or device usedin surgical procedures via either an open incision or percutaneousintroduction into the tissue rather than via an endovascular route. Insome embodiments, the systems and devices of the present disclosure maybe either handheld or a part of a robotically controlled system. In someembodiments, the systems or devices of the present disclosure mayconfigured for handling by a robotic system.

In some embodiments, the size of the components may be varied dependingon the particular procedure. In some embodiments, the rigidity of thecatheters of the present disclosure may be varied depending on the typeof procedure, anatomy to be treated or both. In some embodiments, therigidity may be varied by selecting more rigid components for thecatheter 1601, the guide wire tube 1700 or both.

In reference to FIG. 20, in some embodiments, an optical housing 2002may include multiple channels 2003, 2004 for accommodating multipleguide wire tubes, if more rigidity is required. It should be noted thatin various embodiments, some or all guide wire tubes may include innerlumens in communication with the inner lumens of the catheter 1601 andthe port 1607 of the catheter tip 1606 for passing surgical instrumentsthrough such guide wire tubes. In some embodiments, some or all guidewire tubes may act simply be provided for structural support, and thusmay not include inner lumens.

FIG. 21 illustrates an embodiment of an optical housing 2100 configuredto support multiple light sources 2101 and 2102, which may emit light ofdifferent wavelengths. Having different wavelength sources allows fordifferent functionality within a single catheter or instrument. In someembodiments, the light source 2101 may be selected to emit UV light forfluorescence imaging, while the light source 2102 may be selected toemit white light to allow the user to see and navigate anatomicallandmarks. Bundled together, the user can use the same catheter both fornavigating to the ablation site to ablate tissue, and then to visualizethe ablated tissue. In some embodiments, multiple sources of the samewavelength may be employed. In some embodiments, the optical housing2100 may be configured to support two, three, four or more lightsources.

It should be noted that although the optical housing 1803 is illustratedand describe as supporting a light source and camera, in someembodiments, the housing may be configured to support one or more fiberoptic bundles in communication with an external camera and an externallight source.

The methods, systems and devices disclosed herein can be used for avariety of therapeutic procedures. Exemplary procedures in which themethods, systems and devices disclosed herein can be utilized include,but not limited to, for diagnostic and therapeutic procedures in theheart, for treating arrhythmias, such as, for example, supraventriculararrhythmias and ventricular arrhythmias, for treating atrialfibrillation, and pulmonary vein mapping and ablation.

The presently disclosed methods can be used with two dimensional (2D) tothree dimensional (3D) mapping protocols. A plurality of 2D images canbe superimposed onto a 3D reconstruction image of the tissue or organs,including the heart. Many arrhythmia procedures include the use ofreconstructed three dimension images of the patient's specific anatomyduring the procedure. Using a variety of imaging modalities includingcomputed tomography (CT), magnetic resonance imaging (MRI), ultrasound,and electroanatomical mapping using systems such as NAVX and CARTO. Inall cases, the three dimensional anatomical images or surfaces presentpatient specific anatomy to help target areas of tissue to treat. In allcases, the ability to visualize the precise location where lesions areformed and the precise locations where lesions are missing, e.g., the“gaps” or breaks in the lesion set, would guide the procedure tooptimize the therapeutic outcome. 2D image to 3D image mapping allowsthe system to superimpose, spatially register, and/or texture map singleor multiple images of tissue (that may indicate presence or absence oflesions) with the specific anatomy of the patient in a threedimensional, rotatable, interactive virtual environment.

In some embodiments, the systems and methods of the present disclosureallow the registration and/or overlay of the images produced by thesystem onto the specific anatomy of the patient as seen using otherimaging modalities such as an MRI image, computed tomography (CT) image,ultrasound image and three dimensional reconstructions thereof. In someembodiments, the systems and methods of the present disclosure mayfurther include the registration and/or overlay of the images producedby the system onto the specific anatomy of the patient as seen usingother electroanatomical mapping, anatomical reconstruction, andnavigational systems such as NAVX and CARTO. The registration andoverlay may be performed during the procedure in real time. Texturemapping NADH images onto reconstructed endocardial surfaces permitsvisualization of the treatment site. For example, multiple NADHsnapshots of lesions could create a full panoramic image of the entirepulmonary vein opening, or multiple pulmonary veins. Positioning sensorson the catheter tip could provide information that will allow the NADHimages to be combined together to create a 3D reconstruction image.

While the methods and systems of the present disclosure were describedin connection with a balloon catheter, the methods and systems of thepresent disclosure may also utilize catheters without balloons. Othermeans for displacing blood during fluorescence imaging may be utilized.For example, the catheter of the present disclosure may be provided withan irrigation port through which a fluid can be delivered to the distaltip of the catheter to displace blood away from the tissue being imaged.In some embodiments, the catheter may be introduced through a sheathwhich can infuse a clear fluid capable of displacing blood andtransmitting light. It should of course be understood that, in someembodiments, the means for displacement blood may be combined. Thus, forexample, a balloon catheter as described above can be provided withadditional irrigation port to assist in blood displacement by theballoon.

Examples of using the systems and methods of the present disclosure areprovided below. These examples are merely representative and should notbe used to limit the scope of the present disclosure. A large variety ofalternative designs exists for the methods and devices disclosed herein.The selected examples are therefore used mostly to demonstrate theprinciples of the devices and methods disclosed herein.

EXAMPLES Experimental Procedures

Experiments were performed using animal hearts to compare theeffectiveness of the imaging using NADH recording of the presentdisclosure compared to Triphenyltetrazolium chloride (TTC) staining. Aswill be described in more detail below, the imaging using NADH recordingperformed as good as TTC staining. Importantly, it was done in livingtissue, did not require any additional processing time or the use of adye to achieve the same performance.

Animal Procedures

Ex-vivo experiments were conducted using excised blood-free hearts of arat (200-300 g Sprague-Dawley, n=8) and rabbit (2.5-3.5 Kg New ZealandWhite, n=3). The animals were heparinized and anesthetized usingstandard procedures. Hearts were then excised, the aorta was cannulatedand Langendorff-perfused at constant pressure (50 mmHg) with oxygenated,buffered Tyrode solution at room temperature. The hearts were placed ontop of a grounding pad and submerged in 37° C. Tyrode solution duringablation.

In situ experiments (n=3) were performed using anesthetized open-chestrats (200-300 g Sprague-Dawley). After an IP injection of Telazol (40mg/kg) the hair on the chest and back were shaved, the animal wasimmobilized on a heated platform, and an ablation pad was placed beneaththe animal. Immediately after opening chest cavity, the ablations werecarried out as the exposed epicardial surface was imaged. All anesthesiaand euthanasia procedures were in compliance with the institutionalAnimal Care and Use committee approved protocols.

Ablation Protocols and NADH Recordings

Radiofrequency energy was delivered using a non-cooled blazer catheterwith a 4 mm tip (EP Technologies, Boston Scientific Corporation). Tiptemperatures ranged between 50 to 70° C. The catheter was placedperpendicular to the epicardial surface. Ablation durations varied from15 to 60 sec with a maximum power of 50 W. The epicardial surface wasilluminated with UV light (350/25 nm) using a 100 Watt mercury lamp(Zeiss HBO100 W/2). To record the epicardial fluorescence of NADH, theemitted light was filtered (460/25 nm) and imaged using a CCD camera(Andor Ixon DV860) that has high quantum efficiency for wavelengthscorresponding to NADH fluorescence (80% QE at 460 nm).

Optical Mapping Experiments

Hearts were stained with the potentiometric dye RH237 (Molecular Probes,10 μM solution) and Blebbistatin was added to the perfusate (10 μM finalconcentration) to reduce motion artifact. A dual optical mapping systemcomprised of two CCD cameras (Andor IXON DV860s) fitted with a dual portadapter (Andor CSU Adapter Dual Cam) and a dichroic mirror (610 nm) wasused to image the epicardial fluorescence of RH237 (250-500 fps) andNADH (2 fps) from the same field of view. To record optical actionpotentials, the epicardium was illuminated using two light emittingdiodes (LumiLEDs, 530/35 nm). The resulting fluorescence of RH237 waslong-pass filtered at 680 nm. NADH fluorescence was recorded with theother CCD camera as described above.

The fluorescence of RH237 was processed to subtract backgroundfluorescence from each image and signals for each pixel were normalized.RH237 fluorescence signals were smoothed using a median temporal filter(3 sample width). Isochronal maps of activation times were generated toshow wave front propagation. The average amplitude of optical actionpotentials at each pixel was computed to reveal spatial changes in theamount of electrically active tissue.

TTC Staining

Triphenyltetrazolium chloride (TTC) vital staining is a standardprocedure for assessing acute necrosis Immediately after the imagingprotocol was completed, the tissue was retrogradely perfused through thecoronaries with a 1.0% TTC in Tyrode solution. The heart was thensubmersed in the TTC solution for an additional 8 min. Metabolicallyactive tissue appeared crimson. Necrotic tissue appeared white.

Experimental Results

FIG. 4A, FIG. 4B, FIG. 4C, FIG. 4D and FIG. 4E illustrate RF ablationlesions in blood-free excised rat hearts. The first set of experimentswas conducted in excised hearts from healthy rats of either sex. Heartswere retrograde-perfused with Tyrode solution. The epicardium of 8hearts was ablated and imaged. Two ablation lesions were placed next toeach other on 4 of the hearts. An example of an RF ablation probe in theposition to deliver a lesion onto the epicardial surface is illustratedin FIG. 4A, and the visual appearance of a typical lesion after astandard RFA ablation protocol is illustrated in FIG. 4B. As illustratedin FIG. 4B, ablations caused immediate changes in the visual appearanceof the epicardial surface as a distinct area of pale tissue. Thepaleness corresponds to denaturation of myoglobin at temperatures above60° C. The heart was then placed on a constant pressure perfusion systemand imaged using either a single or dual CCD camera system. FIG. 4Cillustrates the appearance of two distinct RF ablation lesions, asrevealed by fNADH imaging, where partially ischemic tissue appears asblotchy white. As illustrated in FIG. 4C, fNADH images revealed that theareas of ablation appeared markedly dark when compared to thesurrounding unablated myocardium.

After imaging, the hearts were stained with vital dye TTC, which isillustrated in FIG. 4D, and sliced transmurally to examine the ablationlesions, which is illustrated in FIG. 4E. As illustrated in FIG. 4Dafter TTC staining, metabolically active tissue appears red andirreversibly damaged tissue appears white. FIG. 4E illustratestransverse slicing through the heart to show the depth of two lesionsplaced on opposite epicardial surfaces using two different powersettings.

Spatial Extent and Temporal Stability of RF Ablation Lesions.

FIG. 5A and FIG. 5B illustrate lesion stability over time. Specifically,the top row shows snapshots of fNADH at different time points (2-120minutes) after RF ablation. The white box on the top left imageindicates close-up area used in the three lower snapshots, whichillustrate a close-up of the lesion border over three intermediate timepoints (5, 10 and 30 mins).

As shown in FIG. 5A and FIG. 5B, fNADH levels in ablated tissue did notreturn to their pre-ablation values and the size of the lesions did notsignificantly change over the course of the experiments (approx. 2hours). As illustrated by the three lower close-up snapshots in FIG. 5Aand FIG. 5B, areas in the fNADH images that corresponded to the lesionsbecame homogenously dark over time.

As illustrated in FIG. 6A, FIG. 6B and FIG. 6C, the size of the lesionsmeasured from the fNADH images was identical to the size of the areasthat stained negative for TTC. Specifically, FIGS. 6A and 6B illustratesizes of the RF lesions as seen on fNADH-sensitive channel and after TTCstaining. In FIG. 6A snapshots of the three lesions on the surface ofthe rabbit heart respectively illustrate the raw NADH image, invertedNADH image (i.e., the LUT scale of raw fNADH images was inverted to showlesions in white), raw TTC image and black and white TTC image (i.e.,gray scale). The three graphs of FIG. 6B respectively correspond to theintensity profile through each lesion a, b, and c identified in thesnapshots of FIG. 6A. As illustrated by the bar graph of FIG. 6C, widthsof the lesions were not significantly different when examined usingfNADH and TTC staining.

TTC staining is a common method to determine tissue viability. It relieson the ability of dehydrogenase enzymes and NADH to react withtetrazolium salts to form a formazan pigment. Since both methods rely onthe presence of active NADH, the measurement of lesion size is similarfor the two methods. Thus, as illustrated by the graphs in FIG. 6B, liveimaging of NADH fluorescence provides an estimate of the area ofTTC-positive tissue with better than 95% accuracy. From a clinicalperspective, the stability of RF ablation lesions as seen in fNADHimages suggests that UV-based imaging of NADH can be acquired aftermultiple RF ablations have been performed, since lesion appearanceremains stable for several hours.

Identifying Functional Gaps Between RF Ablation Lesions

FIG. 7A, FIG. 7B, and FIG. 7C illustrate dual imaging of epicardialelectrical activity and fNADH of the propagation through narrow isthmusbetween two RF lesions. As discussed above, incomplete lesions may beeven more dangerous if they serve as anatomical routes for reentry andinter-lesion isthmuses as small as 1 mm can lead to recurrentconduction. To study propagation through inter-lesion isthmuseswavefronts of activity between two closely placed RF lesions wereanalyzed. A bipolar pacing electrode was placed on the epicardium abovethe lesions and current was applied at twice the diastolic threshold(2.5 mA). Paced waves caused spontaneous reentrant circuits around thelesions when a functional isthmus was present. An example of thisactivity is illustrated in the sequential snapshots of FIG. 7C. Thethree snapshots in FIG. 7A respectively illustrate an fNADH image oftissue with two lesions, an isochronal map of electrical activity of oneof the reentrant circuits recorded using the voltage-sensitive dyeRH237, and the superposition of the isochronal map on the FNADH image.FIG. 7B illustrates the pseudo ECG trace reconstructed by averagingoptical action potentials from all pixels in individual frame, whichcorresponds to the sequence shown in FIG. 7C. FIG. 7C illustratessequential snapshots of processed RH237 sequence that illustratepropagation of paced beats and reentry around the lesions.

To create the isochronal maps and to reveal propagating wave fronts (asillustrated in FIG. 7A, FIG. 7B and FIG. 7C), optical action potentialswere normalized to show propagating wave fronts in an all-or-nonefashion. This is useful for illustrating propagation but it can bemisleading because it obscures the true optical action potentialamplitudes. To better represent true optical action potentialamplitudes, the RH237 signal at each pixel was scaled as a percentage ofthe maximum optical action potential amplitude for all the pixels.

FIG. 8A, FIG. 8B, FIG. 8C and FIG. 8D illustrate fNADH and electricalactivity across the isthmus between two RF lesions. Specifically, FIG.8A illustrates an x-t representation of the amplitudes of fivesequential action potentials along the black line in the adjacent RH237image. In FIG. 8A the x-axis is the distance between the two lesions andthe y-axis represents time with action potentials indicated by asteriskson the right. FIG. 8B illustrates the graph overlaid on the interlesionintensity profile for fNADH with the profile of the action potentialamplitude. The two profiles had a correlation coefficient of r=0.95,P<0.05. The inter-lesion profile of the optical action potentialamplitude is illustrated in FIG. 8C as an x-t plot for six sequentialbeats, with the x-axis being the distance between the centers of the twolesions. In FIG. 8D the gap is identified by fNADH which gives it alight appearance whereas the ablated lesion is identified by lack offluorescence which gives the tissue a dark appearance. The interlesionprofile of action potential amplitude was then compared to theinterlesion profile of fNADH intensity. The two were highly correlated(r=0.95). These findings suggest that fNADH loss can serve as a directmarker for the diminished functional state of the tissue near theablation site.

Lack of fNADH Indicates Muscle Damage and not Damage to Major CoronaryVessels

Abundant mitochondria that contain NADH make cardiac myocytesparticularly suitable for fNADH imaging. Reduced fNADH at the site ofthe RF ablation lesions indicates loss of myocyte membrane integrity, ascell and mitochondrial membranes are rapidly damaged by thermal stress.Notably, cardiac muscle cell necrosis within the ablation site does notnecessarily mean that the integrity of all underlying structures, suchas coronary vessels, was destroyed. In the experiments a disruption ofmajor coronary vessel structure was not observed. This is because, ifvessels were disrupted, then tissue downstream of damaged vessels wouldbecome ischemic, causing fNADH to increase. Yet, as illustrated in FIG.6A, fNADH levels near the lesions did not significantly change beforeand after ablation. The patches of whiter tissue occasionally seen nearthe ablation site occurred prior to the RF ablation event, potentiallyas a result of transient low perfusion that temporarily caused localischemia. Other evidence of intact coronary structure was thehomogeneity of post-ablation TTC staining: any major vessel damage wouldhave been indicated as areas of unstained tissue outside the RF ablationlesion. However, all of the 13 RF ablation lesions made during theexperiment and identified with TTC were localized strictly to the RFlesion site. Finally, as illustrated in FIG. 4B, observation of intactvessels on the epicardial surface did not indicate severe damage tomajor vessels at the ablation sites.

Conductive Vs. Direct Resistive Heating

FIG. 9A, FIG. 9B, FIG. 9C and FIG. 9D illustrate RH237 retention withinthe ablation area. Specifically, FIGS. 9A-9C illustrate three sequentialsnapshots of rat heart bolus stained with RH237. As illustrated in FIGS.9A-9C, RH237 fluorescence decreases over time, highlighting the lesionsas areas that retain the dye. FIG. 9D illustrates the intensity of RH237staining acquired from the four regions of interest (ROI) identified inFIG. 9A. The solid points, which trend downward over time, correspond toROIs in unablated areas, and the open points, which remain stable overtime, correspond to ROIs in the lesion area.

As illustrated in FIG. 10A, FIG. 10B, FIG. 10C and FIG. 10D, duringoptical mapping the washout rate of RH237 was less within the ablationlesions than in the normal tissue, which resulted in high contrastbetween the lesions and normal tissue in the raw RH237 images. FIG. 10A,FIG. 10B, FIG. 10C and FIG. 10D illustrate RH237 retention after RFablation procedure compared to NADH fluorescence and visual appearanceof the epicardium. FIG. 10A is a schematic representation of lesionformation by RF catheter. FIGS. 10B and 10C illustrate two different rathearts showing a lesion in an fNADH image (the left-hand side image) andthe corresponding RH237 image (the right-hand side image). The scalebars below these images correspond to 5 mm. FIG. 10D illustrates arabbit heart with three RF ablations as it appears within fNADH, RH237images and TTC staining images, with the scale bars below these imagescorresponding to 5 mm. It should be noted that a brownish rim withinwhite TTC channel coincides with RH237 retention area. Importantly, ascan be seen by a comparison of the fNADH and RH237 images in FIG. 10Band FIG. 10C, the diameter of the bright areas of RH237 (correspondingto a lesion) was significantly smaller than the area of the lesionindicated by fNADH. Lesion size in RH237 images corresponded to theinternal ring-like structure often seen on both fNADH and TTC images,such as those illustrated in FIG. 6A.

The most plausible explanation for the bright RH237 areas is the acutedamage to epicardial capillaries that occurs at the site of directresistive heating immediately beneath the RF electrode. This thenreduces washout of the RH237 dye, as can be seen in FIGS. 10B and 10C.RF current heats tissue through resistive heating of a narrow rim oftissue that is in direct contact with the ablation electrode. Deepertissue heating is a result of passive heat conduction from this smallannular volume. Temperatures above 50° C. are required for irreversiblemyocardial injury; at temperatures above 100° C., boiling occurs at theelectrode-tissue contact, forming a coagulum (i.e., the brown rings inFIG. 6A). Direct comparison between two modes of imaging the lesions(fNADH and RH237) may allow direct resistive heating to be distinguishedfrom conductive heat transfer to deeper tissue layers.

RF Lesions in Blood Perfused Rat Hearts

FIG. 11A, FIG. 11B, FIG. 11C and FIG. 11 illustrate a visualization ofRF ablation lesions in blood-perfused open-chest animals. Specifically,FIG. 11A is an open chest brightfield image of a rat heart withepicardial RF ablation lesion, and FIG. 11B illustrates the same heartas observed using fNADH. As illustrated in FIG. 11C, submerging theabove ablated heart in externally added blood completely obscured fNADHsignals. Blood is an optically dense medium and, within the visiblelight band, it interferes with spectroscopic assessment of tissueproperties. Therefore, a critical issue was to show the feasibility offNADH-based imaging in blood perfused animals. This was done by placinglesions on the epicardium immediately after opening the animal's chestand acquiring fNADH images in the same way as the excised heartexperiments. As illustrated in FIG. 11B, major blood vessels appeared asdark tracks within these images, but the RF ablation lesion was clearlyrevealed, which indicated that mitochondria-rich cardiac muscle providesenough fNADH to reveal surrounding unablated tissue. As illustrated inFIG. 11C, the entire field became dark when the epicardial surface ofthe same heart was submerged in blood. As illustrated in FIG. 11D, RFablation lesions were revealed within the fNADH images when blood wasdisplaced from the epicardial surface using a sheet of transparentpolyvinylidene chloride.

FIG. 12 illustrates an ablation lesion obtained from the left atrialtissue of a canine at the time of open heart surgery. The tissue islocated near the area of atrial fibrillation pulmonary vein isolationprocedures. The left atrium was opened surgically and the blood had beenremoved from the field. The animal was in bypass at the time to allowfor normal perfusion of the atrial tissue.

FIG. 13 is an image of an ablation lesion on epicardial surface of rathart after cryo-ablation. This image was obtained from a blood-freeexcised rat heart. Cryoablation was done using liquid nitrogen on a thetip of a metal tip catheter.

FIG. 14 illustrates liver perfused rat tissue that has been acutelyablated using radiofrequency ablation. This was done to illustrate howablation lesions look on the surface of other organs.

FIG. 15 is a 2D image on the right of a standard catheter andreconstruction into 3D integrated into 3D mapping system. A computersystem and program can be used to convert the acquired 2D image of NADHfluorescence into a 3D image superimposed on the atrial anatomy asdisplayed.

In some embodiments, a method for acquiring a real time image of ablatedendocardial heart muscle tissue and unablated gaps at the pulmonary veinand left atrial junction is provided, comprising inflating an inflatablecompliant balloon with transparent fluid for displacing surroundingblood to allow visualization of NADH fluorescence; illuminating with anultra-violet light for exciting mitochondrial NADH of the pulmonary veinand left atrial tissue using UV capable fiber; detecting NADHfluorescence from the illuminated pulmonary vein and left atrial tissueusing optical imaging bundle; creating a fluorescence image with afluorescence camera by filtering the detected NADH fluorescence with 460nm band-pass filter; wherein the detected fluorescence image shows thephysiology of the ablated lesion having a dark appearance due to lack offluorescence, gaps having a light appearance due to normal fluorescence,and any ischemic or injured tissue having a brighter halo typeappearance surrounding the ablated lesion.

In some embodiments, a method for acquiring a real time image of ablatedendocardial heart muscle tissue and unablated gaps at the pulmonary veinand left atrial junction is provided, comprising inflating an inflatablecompliant balloon with transparent fluid for displacing surroundingblood to allow visualization of NADH fluorescence; illuminating withultra-violet light for exciting mitochondrial NADH of the pulmonary veinand left atrial tissue using uv capable fiber; detecting NADHfluorescence from the illuminated pulmonary vein and left atrial tissueusing a CMOS camera; creating a fluorescence image with a fluorescencecamera by filtering the detected NADH fluorescence with 460 nm band-passfilter; wherein the detected fluorescence image shows the physiology ofthe ablated lesion having a dark appearance due to lack of fluorescence,gaps having a light appearance due to normal fluorescence, and anyischemic or injured tissue having a brighter halo type appearancesurrounding the ablated lesion.

In some embodiments, a method of producing visualizations of ablatedlesions in the pulmonary vein area and provide additional informationabout physiology is provided, the method comprising the steps ofilluminating, using an ultraviolet light source, tissue that includesablated tissue and unablated tissue around the ablated tissue; imagingthe illuminated tissue; and producing a display of the imaged,illuminated tissue, wherein the display illustrates the ablated tissueas having less fluorescence than the unablated area around the ablatedtissue. In some embodiments, the display may illustrate areas of highfluorescence surrounded by an area of lower fluorescence or lack offluorescence. In some embodiments, the illustrated areas of highfluorescence surrounded by the area of lower fluorescence indicate thatthe areas of high fluorescence are not ablated. In some embodiments, thefluorescence is caused by NADH in the illuminated tissue. In someembodiments, the illumination, imaging and producing are performed whilea radio frequency, cryoablation or laser catheter is used to ablate thetissue. In some embodiments, the illumination and imaging are performedusing a fiber optic waveguide coupled to a tip of the lumen catheter,the fiber optic waveguide delivers ultraviolet light from theultraviolet light source to the illuminated tissue. In some embodiments,the tissue is heart tissue. In some embodiments, the imaging of theilluminated tissue is performed without addition of chemicals to theilluminated tissue.

In some embodiments, a method of treating Atrial Fibrillation (AF) isprovided, the method comprising the steps of ablating a portion of theatrial tissue; illuminating tissue using an ultraviolet light source;imaging the illuminated tissue using fluorescence camera and a filterfor allowing visualization of fluorescence; producing a display of theimaged illuminated tissue; identifying gaps between ablated tissue basedon the display of the imaged illuminated tissue; wherein ablated tissueis identified by lack of fluorescence which gives the tissue a darkappearance and wherein gaps constituting unablated tissue are identifiedby fluorescence which gives them a light appearance and ablating theidentified unablated tissue gaps between ablated tissue. In someembodiments, the display illustrates the ablated tissue as having lessfluorescence than the gaps.

In some embodiments, a system for imaging tissue includes a catheterhaving a distal end and a proximal end; an inflatable balloon disposedabout the distal end of the catheter; and an optical housing extendingfrom the distal end of the catheter into the balloon, the opticalhousing being configured to position inside the balloon a light sourcefor illuminating a tissue outside the balloon and a camera for imagingthe illuminated tissue.

In some embodiments, a system for imaging tissue includes a catheterhaving a distal end and a proximal end; an inflatable balloon disposedabout the distal end of the catheter; and an optical housing extendingfrom the distal end of the catheter into the balloon; a light sourceinside the balloon, the light source being supported by the opticalhousing and configured to excite native reduced form of nicotinamideadenine dinucleotide or nicotinamide adenine dinucleotide hydrogen(NADH) in a tissue; and a camera inside the balloon, the camera beingsupported by the optical housing and configured to image the tissueilluminated by the light source.

In some embodiments, a system for imaging tissue includes a catheterhaving a distal end and a proximal end; an irrigation port to displaceblood with a fluid about the distal end of the catheter; and an opticalhousing extending from the distal end of the catheter, the opticalhousing being configured to support a light emitting diode light sourcefor illuminating tissue and a visualization device including a pluralityof image sensors that convert an optical image into an electronic signalfor imaging the illuminated tissue.

In some embodiments, a system for imaging tissue includes a sheath forinfusing a fluid capable of displacing blood and transmitting light; acatheter disposed within the sheath, the catheter having a distal endand a proximal end; an optical housing extending from the distal end ofthe catheter, the optical housing being configured to support a lightemitting diode light source for illuminating tissue and a visualizationdevice including a plurality of image sensors that converts an opticalimage into an electronic signal for imaging the illuminated tissue.

In some embodiments, a method for imaging tissue includes advancing to atissue a catheter comprising an inflatable balloon disposed about thedistal end of the catheter and an optical housing extending from thedistal end of the catheter into the balloon to position a light sourceand a camera inside the balloon; ablating the tissue; illuminating withthe light source an area of tissue including tissue treated by ablationand surrounding tissue to excite NADH in the area of tissue; imagingwith an imaging device the area of tissue to detect NADH fluorescence ofthe area of tissue; and producing a display of the imaged, illuminatedtissue, the display illustrating ablated tissue as having lessfluorescence than non-ablated tissue.

The foregoing disclosure has been set forth merely to illustrate variousnon-limiting embodiments of the present disclosure and is not intendedto be limiting. Since modifications of the disclosed embodimentsincorporating the spirit and substance of the disclosure may occur topersons skilled in the art, the presently disclosed embodiments shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

What is claimed is:
 1. A system for imaging tissue comprising: acatheter having a distal end and a proximal end; an inflatable balloondisposed about the distal end of the catheter; and an optical housingextending from the distal end of the catheter into the balloon, theoptical housing being configured to position inside the balloon a lightsource for illuminating a tissue outside the balloon and a camera forimaging the illuminated tissue.
 2. The system of claim 1 furthercomprising an ablation member having an energy source selected from thegroup consisting of radiofrequency energy, microwave energy, electricalenergy, electromagnetic energy, cryoenergy, laser energy, ultrasoundenergy, acoustic energy, chemical energy, and thermal energy.
 3. Thesystem of claim 1, wherein the light source is a UV light emitting diode(LED).
 4. The system of claim 1, wherein the camera includes imagesensors that convert an optical image into an electronic signal.
 5. Thesystem of claim 1, wherein the system is robotically controlled. 6.(canceled)
 7. (canceled)
 8. (canceled)
 9. The system of claim 1 furthercomprising a support tube extending beyond the distal tip of thecatheter to provide a structural support for the balloon.
 10. The systemof claim 9 further comprising a tip around a distal end of the supporttube, the tip being configured to act as an ablation element.
 11. Thesystem of claim 9, wherein the support tube includes an inner lumen incommunication with an inner lumen of the catheter for passing anablation member distally of the balloon.
 12. The system of claim 1,wherein the catheter is configured for an endovascular approach to thetissue.
 13. (canceled)
 14. The system of claim 1, wherein the lightsource is configured to excite native reduced form of nicotinamideadenine dinucleotide (NADH) in the tissue.
 15. The system of claim 1further comprising a first light source and a second light sourcecapable of generating light of a different wavelength than the firstlight source.
 16. The system of claim 1 further comprising a displaysystem connected to the camera for generating an image of theilluminated tissue based on the detected NADH fluorescence. 17.(canceled)
 18. (canceled)
 19. A system for imaging tissue comprising: acatheter having a distal end and a proximal end; an inflatable balloondisposed about the distal end of the catheter; and an optical housingextending from the distal end of the catheter into the balloon; a lightsource inside the balloon, the light source being supported by theoptical housing and configured to excite NADH in a tissue; and a camerainside the balloon, the camera being supported by the optical housingand configured to image the tissue illuminated by the light source. 20.(canceled)
 21. The system of claim 19, wherein the camera is configuredto detect NADH fluorescence of the tissues illuminated by the lightsource.
 22. The system of claim 19 comprising a second light source forproviding white light.
 23. (canceled)
 24. (canceled)
 25. A method forimaging tissue comprising: advancing to a tissue a catheter comprisingan inflatable balloon disposed about the distal end of the catheter andan optical housing extending from the distal end of the catheter intothe balloon to position a light source and a camera inside the balloon;ablating the tissue; illuminating with the light source an area oftissue including tissue treated by ablation and surrounding tissue toexcite NADH in the area of tissue; imaging with an imaging device thearea of tissue to detect NADH fluorescence of the area of tissue; andproducing a display of the imaged, illuminated tissue, the displayillustrating ablated tissue as having less fluorescence than non-ablatedtissue.
 26. The method of claim 25, wherein the tissue is a heart muscletissue.
 27. (canceled)
 28. The method of claim 25 further comprisingablating additional injured tissue identified by distinguishing betweenthe ablated tissue and the injured tissue based on the amount offluorescence.
 29. The method of claim 25 further comprisingdistinguishing between tissue that is no longer electrically conductiveand tissue that remains electrically conductive.
 30. The method of claim25 further comprising distinguishing between ablated tissue, edematoustissue, and non-ablated tissue. 31.-33. (canceled)